Jenna Nickerson is a sheriff's deputy in Superior, Nebraska.
When a creature infected by the darkness who was approaching Sam and Dean Winchester, she shot it, saving the brothers. She reveals that she was injured, and the Winchesters drive Mike Schneider to Nuckolls County Medical Center. They use a wheelchair from outside the hospital to help her into the building, where Dean stitches up her wound.
When Sam rejoins them, he is followed by Mike and his baby. Sam then finds out that Mike had been infected and Jenna tells them that she believes he should be allowed to remove himself from the group before he turns fully into a monster. Mike agrees, knowing that the creatures eventually die of an unknown cause after a certain period of time. He entrusts Jenna with the baby as he says goodbye.
When Castiel calls Sam and Dean, she comes to the realization that they are not FBI agents and they confess to lying. Sam then decides to use himself as bait to distract the monsters who are rapidly closing in, and Jenna and Dean escape with the baby. They are stopped by Mike who seems as though he wants the baby but only wants to tell them that her name is Amara.
After taking Amara to her grandmother's house, they notice that Amara is levitating blocks and she calls Dean back while her religious grandmother calls an exorcist. Jenna is surprised to learn that Dean and Father Crowley know each other. As the two talk outside, Jenna checks on Amara then murders her grandmother by slitting her throat. Dean and Crowley find her smashing her grandmother's angel figurines and Crowley realizes that Amara consumed Jenna's soul. Jenna attacks Dean before a bored Crowley flings her into the celling then drops her to the floor. Jenna's neck breaks in the fall and she dies, leaving Dean annoyed that Crowley killed her.
- Jenna's actor, Laci J. Mailey, also portrayed Emily in There Will Be Blood.
- Jenna reveals that her first kiss was a girl.